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Currently, the Kyber elevator allocates its private data dynamically in ->init_sched and frees it in ->exit_sched. However, since ->init_sched is invoked during elevator switch after acquiring both ->freeze_lock and ->elevator_lock, it may trigger the lockdep splat [1] due to dependency on pcpu_alloc_mutex. To resolve this, move the elevator data allocation and deallocation logic from ->init_sched and ->exit_sched into the newly introduced ->alloc_sched_data and ->free_sched_data methods. These callbacks are invoked before acquiring ->freeze_lock and ->elevator_lock, ensuring that memory allocation happens safely without introducing additional locking dependencies. This change breaks the dependency chain involving pcpu_alloc_mutex and prevents the reported lockdep warning. [1] https://lore.kernel.org/all/CAGVVp+VNW4M-5DZMNoADp6o2VKFhi7KxWpTDkcnVyjO0=-D5+A@mail.gmail.com/ Reported-by: Changhui Zhong <czhong@redhat.com> Reported-by: Yi Zhang <yi.zhang@redhat.com> Closes: https://lore.kernel.org/all/CAGVVp+VNW4M-5DZMNoADp6o2VKFhi7KxWpTDkcnVyjO0=-D5+A@mail.gmail.com/ Tested-by: Yi Zhang <yi.zhang@redhat.com> Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Yu Kuai <yukuai@fnnas.com> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.